The long term objective of the research is to understand the nature of aphasic impairments in sentence comprehension, in particular the use of syntactic structure to determine sentence meaning, and the way the processes involved in sentence comprehension are organized in the brain. This project will examine aphasic patients with single strokes for their abilities to use differentsyntactic structures to determine aspects of sentence meaning, testing their use in a number of tasks. The result of these behavioral studies will be a detailed picture of what a patient can understand, and how s/he processes syntactic structures as s/he hears them (on-line processing) as well as when a sentence is over (off-line processing). We will obtain MR images of the structure and perfusion of regions of the patients' brains, and will identify the areas affected by the stroke, using modem analysis methods. Wewill then look for the brain regions in which lesion size accounts for significant amounts of the variance in performance. In the course of the research, we will provide data regarding both questions about the behavioral natureof sentence comprehension impairments (such as whether individual patients lose the ability to accomplish particular syntactic operations or whether their difficulties are best viewed as due to pathological limitations in their ability to accomplish operations in general, which affect more complex structures first), and about neural issues, such as whether aspects of the sentence comprehension process are always located in the same brain regions in all individuals. The results could have important consequences for howwe think of these disorders and the neural organization that supports these functions.